Complementary metal-oxide semiconductor (CMOS) devices typically employ at least one gate which is separated from a channel (or channels) of the device by a gate dielectric. The gate dielectric is commonly an oxide material. Conventionally, gate oxides are formed using a thermal oxidation process. Thermal oxidation works well when the material on which the oxide is being formed is pure silicon.
However, when thermal oxidation is employed on substrates other than pure silicon (Si), the resulting oxide may not be a suitable gate dielectric material. For instance, when the thermal oxide is grown on a silicon germanium (SiGe) substrate, the germanium (Ge) can become incorporated into the growing oxide. Ge oxidizes faster than silicon and can cause a separation of the Si and Ge. Also, Germanium oxide (GeO2) is unstable and soluble in water, both of which are undesirable properties for a gate dielectric.
Accordingly, improved gate dielectric fabrication processes would be desirable.